Re: differential probes

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>

Hi Malcolm,

At 08:29 AM 7/17/2003 +1200, you wrote:
>On 16 Jul 2003, at 6:33, Tesla list wrote:
>
> > Original poster: "Daniel Barrett by way of Terry Fritz 
> <teslalist-at-qwest-dot-net>" <dbarrett1-at-austin.rr-dot-com>
> >
> >      Hi All!
> >      Just a thought here- This spark gap section could really just be 
> part of
> > the PC layout: Route the potentially high current signals with maybe 10 mil
> > tracks, separated from each other by an inch, but "T" off a spark gap
> > between these tracks. That way an arc will occur in a controlled spot 
> on the
> > board and the feeding traces will be small enough to vaporise. Should
> > provide an easy to make fuse, but I guess the board would need a lot of
> > rework between accidents ;)
> > db
>
>The problem I see with that (and I've seen it numerous times in
>equipment servicing) is that the arc will continue, carbonizing the
>board material which might well render the board throwaway material.
>
>Malcolm
>

The protection stuff is really to just try and save the scope.  At that 
point, the probe itself is expendable...

I sort of don't like the PCB spark gap idea since the breakdown voltage is 
pretty "iffy".  Any contamination, and goodness knows where it will 
arc.  Small balls (like BBs) will at least be somewhat predictable and robust.